Picture-transmission system



March 25, 1930.

F. SCHROTER 1,751,606

PICTURE TRANSMISSION SYSTEM Filed May 25, 1928 INVENTQ 12 SCHRO BY ORNEYPatented Mar. 25, 1930 UNITED STATES PATENT OFFICE FRITZ SGHBbTEB, OFBERLIN, GERMANY, ASSIGNOR TO GESELLSCHAFT FER DRAHT- LOSE TELEGRAPHIE M.B. H. HALLESCHES, BERLIN, GERMANY, A CORPORATION OF GERMANYPICTURE-TRANSMISSION SYSTEM Application filed Kay 25, 1928, Serial No.280,471, and in Germany June 10, 1927.

The present invention particularly relates to the reproduction ofpictures and the like in television work and particularly concernsitself with, and has as its principal object,

that of increasing the amount of available light upon the reproduced imae.

With a view to increase the uminosity of the incoming picture, inaccordance with my invention the Nipkow disk at the receiver,

19 operating in synchronism with the picture scanning or exploring meansat the transmitter end assumes a modified form. Instead of the diskholes having each the size of a pictnre element or unit and disposedalon an Archimedean spiral, a number of puncti orm glow-discharge lampsare distributed about the disk in a manner corresponding to the usualdisk holes, and of these various lamps only that particular lamp is.connected in the receiving circuit which happens to pass through thefield of the picture.

To produce the television picture at the receiving end, according toschemes disclosed in the earlier art, a Nipkow disk is used in such amanner that a field of brightness controlled in a way free from inertiais viewed through the holes in the disk. In this case the field is ofthe size of the entire picture and was of uniform luminous density 80throughout. As a result, only a correspondingly small fraction of theentire light furnished by the light-control or valve means is able topass through any given hole of the disk, and the result is that the meanbright- 85 ness of the perceivable picture is extremely low.

According to the disclosures of the present invention, a considerableincrease in 111 minosity is obtained by concentrating all availablelight upon a picture element. The

fundamental scheme underlyin such an arrangement of this character is sown by Fig. 1 of the accompanying drawing, while Figs. 2

. and 3 illustrate special embodiments in longitudinal section of theglow-discharge or gllm lampsfor carrying out the complete arrangement ofFig. 1. i

Referring to Fig. 1,1 denotes the Ni kow disk revolving in synchronismin accor ance with well-known schemes with the transmitter device. TheNipkow disk rotates about the driving spindle 2. The dimensions orcontour of the field of the picture is indicated by field 3 by dashlines. In lieu of the simple perforations, the similarly positionedpunctiform glow-discharge lamps I, II, III, are provided. .Theseglow-lamps are associated by leads a, b, c, with corresponding segmentsA, 13,0, of a commutator revolving conjointly with the disk. Single-poleconnection wlth the commutator is sufficient, since the second pole ofall lamps is united with the metallic mass of the disk which isconnected wlth the receiver amplifier by way of lead 8, the stationaryslide contact 5 and slip ring 6. The stationary contact 4 feedstheamplified incomlng currents alternately to the various segments A, B,C, etc., and thus to the electrodes of equal polarity of theglow-discharge lamps I, II, III, etc. As a result of th1s arrangement,only one glow-discharge lamp at any given instant is connected in thereceiver circuit, or, to be more precise, that lamp which happens topass through the picture field. Hence, the whole current subject to thecontrol of the transmitter is concentrated upon a single picture orsurface element, whereas according to earlier schemes it had to beuniformly distributed overthewhole picture surface 3.

A suitable embodiment of a punctiform glow-discharge lamp is shown byway of example in Fig. 2. Soldered in disk 1 are metallic bushes, andinto the latter the glowdischarge lamps 9 are fitted in an adjustablemanner, the light suitably leaving through a plane-parallel window 10secured by cement in front. Each of the lamps is furnished with a hollowcathode 11 and a co-axial anode 12 carefully insulated therefrom. By thediaphragm-like form .of construction of the electrodes as shown,concentration of the discharge current and the incandescence producedthereby upon a very small area corresponding to a picture element isinsured, or, in other words, a cone of rays exactly defined in itsboundaries is allowed to issue from the lamp. The electrode seals orlead-ins are indicated at 13 and 14, and the lead to the anode forinstance, in all of the lamps is brought to the metallic mass of thedisk by soldering wire 14 at point 16. The cathode lead is brought byway of 17 to the revolving commutator.

In order to avoid lags in discharge, it may be a good plan to maintainin all lamps a very feeble auxiliary discharge which furnishes so littlelight that the dark portions of the picture will not be appreciablyilluminated. The connection and the arrangement of such a lamp is shownby way of example in Fig. 3, where 9 denotes again the cylindrical glassbulb of the lamp, 10 the outlet window, 12 the anode having diaphragm orscreen-like action, 11 the cylindrical hollow cathode with supply lead13. Fitted over the cathode in an insulated manner is a carefullycentered issuin diaphragm for the discharge current. 19 esignates anauxiliary electrode for insuring a permanent auxiliary discharge uponwhich the amplified incoming current is superposed.

The above described scheme operates in this manner that, apart from-therevolving commutator which is supplied with current from the receiveramplifier 20 by way of the stationary brush 4 and which feeds thecurrent consecutively to the different anodes 12, there is provided asecond common supply lead from an auxiliary potential source 21 by wayof a slip brush 22, a slip ring and high resistance 24 to the variousauxiliary electrodes 19. The return lead from the cathode 11 is broughtby way of a slide contact 5 which is in contact with slip ring 6. Inthis arrangement, all of the auxiliary electrodes 19 of theglow-discharge lamps are connected by way of high series resistances 24permanently with the potential source 21, with the result that in all ofthe lamps, a feeble current adapted to preclude lag in the discharge iscaused to flow permanently from the auxiliary electrode 19 through thediaphragm hole of screen or diaphragm 18 to the cathode 11, while thecurrent impulse furnished from the receiver amplifier 20 and causing thebright flash of the lamp at the different points of the picture flows byway of 4 and 12 to 11.

In the forms of construction of the glowlamp in Fig. 2 and Fig.3, theinternal construction of the same, of course, must be sufficientlystable in order to offer suflicient resistance to the centrifugal actionproduced by rapid rotation, which is insured by con-.

venient propping of the electrodes on electrode holders or anchors. Forexample, the diameter of the cylindrical lamp bulb, ac-

cording to Fig. 2, may be chosen so narrow that anode 12 havingcylindrical shape is in direct contact with the bulb wall, if necessary,with the interposition of thin layers of a sufliciently yieldingsubstance. Since the weight of the lamps can be made very small (say,from 5 to 10 grams), the rotation of the disk being at the rate of 10 to20 revolutions per second will not result in centrifugal forces liableto endanger or tax the solidity of the construction. The electrodesinside the glow-discharge lamps can be accurately centered. Thus, ifinside the carrier bushes for the diflerent lamps, means adapted toallow of slight displacements in the form of a well-known adjustablenature are provided', then the different light points can be so set thatthe picture lines in the field of the picture will be exactly fittingtogether.

The advantage offered by this arrangement resides in that the eyereadily perceives a very luminous picture, particularly because thelight rays are not made to pass first through optical means conducive tolosses. The luminous points can be kept at a diameter less than mm. sothat, for the purpose of reducing the dimensions of the rotating disk tothe absolute minimum, the picture field can be kept within smalldimensions. The picture in this case is viewed through a magnifyingoptical outfit which is placed in front of the disk in the direction ofthe view.

Instead of the form of construction comprising glow-discharge lamps ashereinbefore described, of course, also other luminous sources adaptedto the object of the invention could be employed.

Having now described my invention, I claim:

1. A system for reproducing images which includes means for receivingsignals correspondlng to varying picture densities, a disk, a pluralityof light sources arranged in spiral formation about said disk andsupported thereby, means for rotating said disk in synchronism with acorresponding element at a transmitting station, means associated withsaid signal receiving means for sequentially flashing said light sourcesin accordance with said. received signals, and means for maintaining apermanent biasing potential upon all of said light sources for thepurpose of maintaining an auxiliary discharge and eliminating theeffects of lag in the periodic flashing of said light sources.

2. A system for reproducing images which includesa disk, a plurality oflight sources carried by said disk and arranged in spiral formationabout the marginal portion thereof, means for rotating said disk andsuccessively passing each of said light sources through a predeterminedimage reproducing FRITZ SCHRCTER.

